A wobble plate type compressor which reciprocates pistons by converting the rotational movement of a cam rotor into nutational movement of a wobble plate is well known in the art. Changing the inclined angle of the wobble plate changes the stroke of the pistons and therefore changes the displacement volume of the cylinder. In U.S. Pat. Nos. 3,062,020 and 4,061,443, a wobble plate is proximately disposed on a variable angle rotating cylindrical member. The cylindrical member is hingedly connected to a rotor which is fixed on the drive shaft. The rotor permits varying the inclined angle of the cylindrical member. Movement of the cylindrical member is controlled by the pressure difference between the crank chamber and the suction chamber. In this structure the rotor is connected to the cylindrical member only by the connecting hinge mechanism; therefore, the varying angle of the cylindrical member is not stable.
One solution to this problem is shown in U.S. Pat. No. 4,061,443 which uses a slider element. The slider element is slidably disposed on the drive shaft and is coupled to the cylindrical member through a pin extending from the slider element. The angle of the cylindrical member is therefore determined by the sliding motion and the location of the slider element.
Furthermore, in an axial piston type compressor, the acting point of the piston gas pressure on the cylindrical member is shifted from the top dead center point of the piston, and is eccentrically located in the direction perpendicular to the surface of the angle of the inclined surface of the cylindrical member. This is best illustrated in FIG. 1 where S is the inclined surface, D is the top dead center point of the piston, O is the driving axis line, P1 is the direction of the angle of the inclined surface, P2 is the direction perpendicular to P1, and F is the piston gas pressure. As shown in FIG. 1, the piston gas pressure acts eccentrically on the inclined surface. A moment is generated to rotate the inclined plate around P2. Another moment is generated to rotate the cylindrical member around P1. To accommodate these moments, the supporting structure for the cylindrical member must be highly rigid.
In the structure shown in U.S. Pat. No. 4,061,443, in order to increase the strength of the support mechanism the support structure becomes larger and more complicated. In order to accommodate this enlarged support structure, the compressor must be larger.